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bpf: add bpf_get_hash_recalc helper 

If skb_clear_hash() was invoked due to mangling of relevant headers and
BPF program needs skb->hash later on, we can add a helper to trigger hash
recalculation via bpf_get_hash_recalc().

The helper will return the newly retrieved hash directly, but later access
can also be done via skb context again through skb->hash directly (inline)
without needing to call the helper once more.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2016-07-03 01:28:47 +02:00 committed by David S. Miller
parent 6fd980ac39
commit 13c5c240f7
2 changed files with 28 additions and 0 deletions
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9
include/uapi/linux/bpf.h
View File

@ -348,6 +348,15 @@ enum bpf_func_id {
* < 0 error
*/
BPF_FUNC_skb_in_cgroup,
/**
* bpf_get_hash_recalc(skb)
* Retrieve and possibly recalculate skb->hash.
* @skb: pointer to skb
* Return: hash
*/
BPF_FUNC_get_hash_recalc,
__BPF_FUNC_MAX_ID,
};

19
net/core/filter.c
View File

@ -1729,6 +1729,23 @@ static const struct bpf_func_proto bpf_get_route_realm_proto = {
.arg1_type = ARG_PTR_TO_CTX,
};
static u64 bpf_get_hash_recalc(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
{
/* If skb_clear_hash() was called due to mangling, we can
* trigger SW recalculation here. Later access to hash
* can then use the inline skb->hash via context directly
* instead of calling this helper again.
*/
return skb_get_hash((struct sk_buff *) (unsigned long) r1);
}
static const struct bpf_func_proto bpf_get_hash_recalc_proto = {
.func = bpf_get_hash_recalc,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
};
static u64 bpf_skb_vlan_push(u64 r1, u64 r2, u64 vlan_tci, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *) (long) r1;
@ -2337,6 +2354,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
return &bpf_redirect_proto;
case BPF_FUNC_get_route_realm:
return &bpf_get_route_realm_proto;
case BPF_FUNC_get_hash_recalc:
return &bpf_get_hash_recalc_proto;
case BPF_FUNC_perf_event_output:
return bpf_get_event_output_proto();
case BPF_FUNC_get_smp_processor_id: